Technical Field
The disclosure is related to a subframe scheduling scheme in the Time Division Duplex—Frequency Division Duplex (TDD-FDD) joint system, and more particular to a timing scheme for the cross-carrier scheduling in the TDD-FDD Long Term Evolution (LTE) system, and specifically to a transmission method and device in a TDD-FDD joint system.
Related Art
The traditional LTE (Long Term Evolution) system of 3rd Generation Partner Project (3GPP) defines two duplex modes, which are Frequency Division Duplex (FDD) system and Time Division Duplex (TDD) system respectively. FDD adopts frame structure 1, while TDD adopts frame structure 2. The difference between FDD and TDD lies in that each subframe of FDD frame configuration is 1 millisecond, while the TDD system defines 1 to 2 special subframes in one frame (10 subframes). The special subframes are composed of a downlink synchronous time slot, a guard period and an uplink synchronization time slot. 3GPP defines the frame configuration for the TDD-LTE system, as shown in Table 1, in which D indicates downlink subframe, U indicates uplink subframe, and S indicates special subframe.
TABLE 1TDD LTE Frame ConfigurationDownlink-TDD to-UplinkFrameSwitch-pointSubframe Index No.ConfigurationPeriodicity01234 56 78 90 5 ms DSUUUDSUUU1 5 msDSUUDDSUUD2 5 ms DSUDDDSUDD310 msDSUUUDDDDD410 msDSUUDDDDDD510 msDSUDDDDDDD6 5 ms DSUUUDSUUD
3GPP further defines the uplink scheduling delay k for the cross-subframe, as shown in Table 2. The meaning of k is: for Downlink Control Information (DCI) used for uplink scheduling in the downlink subframe n, the scheduling subframe is on the subframe n+k. It should be noted that for TDD frame configuration #0, k is as shown in Table 2, or 7, or as shown in Table 2 and 7 simultaneously, which may be configured via the uplink index (ULI) in DCI.
TABLE 2Scheduling Parameter k of the uplink subframe in TDD LTETDD Frame Subframe Index No.Configuration012 34567 890464616464244344444454677775
When the Physical Uplink Shared Channel (PUSCH) is scheduled according to the frame configuration #0 (for example, the uplink reference DL/UL frame structure in the above scheme is #0), the two-bit uplink index (ULI) is defined in the DCI to indicate the index of the uplink subframe scheduled by the DCI. It should be noted that the two bits are used for Downlink Assignment Index (DAI) instead of being used as ULI for the non-zero frame configurations. That is, the two bits are used to indicate the amount of Physical Downlink Shared Channel (PDSCH) represented by the uplink ACK/NACK corresponding to the DCI. For the ACK/NACK reported on the uplink subframe n, the targeting PDSCH can only be PDSCH indicated by DCI sent on the subframe n−k, wherein k belongs to the subframe set K, as defined in Table 3.
TABLE 3Downlink Associating Subframe Set KTDD FrameConfig-Subframe Index nuration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7,——4, 63——7, 6, 116, 55, 4—————4——12, 8, 7, 116, 5, 4,——————75——13, 12, 9, 8,———————7, 5, 4, 11,66——775——77—
In LTE system, the communication between the base station and the user equipment (UE) is scheduled by Physical Downlink Control Channel (PDCCH). The information transmitted on PDCCH is Downlink Control Information (DCI). Further, DCI is divided into uplink-scheduling DCI and downlink-scheduling DCI. The former schedules the UE to transmit uplink data, and the latter schedules the UE to receive downlink data. As of 3GPP Release 11 (R11), DCI formats {0, 4} are for uplink-scheduling DCI, DCI formats {1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 2D} are for downlink-scheduling DCI, and DCI formats {3, 3A} are for adjusting uplink transmission power. For the TDD system, DCI includes additional bits (that is the additional bits do not occur in FDD system). For example, Downlink Assignment Index (DAI) or Uplink Index (ULI) of two bits, sounding Reference Signal Request of one bit of partial DCI format (2B, 2C, 2D), or Hybrid Automatic Repeat Request (HARQ) process number of additional one bit. Therefore, under the same system configuration and DCI format, DCI in the TDD system usually has additional two to four bits compared to the DCI in FDD system.
In order to improve the peak rate of communication and provide greater flexibility in scheduling, 3GPP introduces Carrier Aggregation (CA) technology, that is to allow UE to simultaneously receive and send data on more than one carrier. When the UE is configured with more than one carrier, one of the carriers is Primary Carrier Component (PCC), and the others are Secondary Carrier Component (SCC). Further, the cross carrier scheduling technology is introduced to 3GPP, that is DCI has Carrier Indicator Field (CIF) of additionally three bits for indicating which candidate carrier is the carrier scheduled by DCI. The CIF value of PCC is fixed to 0. The system configures that whether the current DCI includes CIF or not thorough the high layer signaling. The UE reads the high layer signaling on PCC to obtain the system information of PCC and SCC. The high layer signaling is Radio Resource Control (RRC) layer signaling.
The traditional CA is performed internally in the same duplex mode, that is multiple TDD carriers are aggregated or multiple FDD carriers are aggregated. 3GPP RAN #60 plenary approved a newstudy item: LTE TDD-FDD Joint Operation, that is a UE may access TDD and FDD network simultaneously to obtain higher communicate rate or better communication experience. One intuitive solution is to expand the tranditional carrier aggregation scheme to TDD-FDD Joint Operation, that is the carrier aggregation scheme is performed between TDD carrier and FDD carrier.
When a FDD carrier is adopted as scheduling CC, and a TDD carrier is adopted as scheduled CC, the timing of the cross carrier scheduling requires special design. The scheduling timing includes uplink scheduling timing and downlink scheduling timing. The uplink scheduling timing includes the timing relationship among the various steps: the base station transmits uplink-scheduling DCI, the UE transmits data on PUSCH according to the DCI, the base station transmits ACK/NACK on Physical HARQ Indicator Channel (PHICH), and the UE transmits data on PUSCH according to the ACK/NACK. The downlink scheduling timing includes the timing relationship of the following steps: the base station transmits the downlink-scheduling DCI and data, and the UE reports uplink ACK/NACK.